Electrostatics

Electrostatic Precipitators

So what's an Electrostatic Precipitator?

"An Electrostatic Precipitator (ESP) is a device that uses electrical forces to remove unwanted particles or liquid droplets from a flow of gas." (Blake, Leesa et al.) ESP's are very effective devices and can get rid of over 99% of pollen, bacteria, viruses, fungi, hairs, aerosols and smoke from an environment. Normally, ESP's are used in large manufacturing buildings to reduce the amount of pollution that is released into the atmosphere but smaller versions can also be placed in homes to improve the air quality (Hoffman, Matt).

How is Electrostatics involved?

As particles pass through the machine, they become charged when coming in contact with a positive wire. They are then attracted to oppositely charged collection plates and are deposited there and become neutralized. When enough dust has gathered on them, the collection plates are shaken and the particles fall into containers called hoppers.


One of the major problems of this machine is how to extract the collected dust particles from the collection plates without them re-entering the airstream of purified gas. This is accomplished by rapper (metal hammers) that deliver vertical shock waves every so often that causes the dust particles to be sheared off into the collection containers and away from the newly cleaned air.


(PPC, Air Pollution Control)

Basic Principles

Ionization - charging of particles

Migration - transporting the charged particles to the collecting surfaces

Collection - accumulation of the charged particles onto the collecting surfaces

Charge Dissipation or Discharge - neutralizing the charged particles on the collection surfaces

Particle Dislodging- getting rid of the particles from the collection surfaces into the hopper bins

Particle Removal - transporting the particles from the hoppers to a disposal point


(Neundorfer, Inc.)


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Resource: Kurtus, Ron

www.school-for-champions.com

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(a) Schematic of an electrostatic precipitator. Air is passed through grids of opposite charge. The first grid charges airborne particles, while the second attracts and collects them. (b) The dramatic effect of electrostatic precipitators is seen by the absence of smoke from this power plant. (Credit: Cmdalgleish, Wikimedia Commons) (resource: http://cnx.org/content/m42329/latest/?collection=col11406/latest)




Still need help understanding?

Works Cited

U.S. Environmental Protection Agency. Particulates - Electrostatic Precipitators. U.S. Environmental Protection Agency, January 29th, 2010. Website. February 10th, 2013.
http://www.epa.gov/eogapti1/course422/ce6a1.html



Blake, Leesa; Mazza, Michael; Mills, Alex; Mustoe, Frank; Ross, Jim; Stiff, Thomas. ON Science 9. Toronto: McGraw-Hill Ryerson Limited, 2009. Print.



Hoffman, Matt. “Choosing the Right Technology for Clean Indoor Air”. Occupational Hazards. 05-01-2004.



OSC Physics Maintainer. Connexions. Rice University, July 5th 2012. Web. February 20th, 2013.



Neundofer, Inc. Neundofer: Particulate Knowledge. Neundofer, Inc., n.d. Web. February 20th, 2013.



Braza, Rolando. "What Is an Electrostatic Precipitator?" WiseGeek. Ed. C. Wilborn. Conjecture, 04 Feb. 2013. Web. 20 Feb. 2013.

http://www.wisegeek.com/what-is-an-electrostatic-precipitator.htm